Valentino Rossi says his Yamaha team needs to "be very careful" with Marc Marquez despite the MotoGP world champion's deficit in the championship.
Honda rider Marquez is fourth in the standings, 74 points behind Rossi, not having won a race since Austin, the second round of the season.
The Spanish rider fought for victory with Rossi at Assen 10 days ago, but it was the Italian who emerged victorious after a controversial last-lap move.
Rossi reckons Marquez will be a threat again now he has made a step forward with his bike's set-up.
"I'm ready for Sachsenring and am going into this race weekend with a happy mindset," said Rossi ahead of this weekend's German GP.
"I managed to recover a bit of an advantage that I had lost in past races.
"Having a 10-point lead after eight races is not bad, I'm very happy. Now we go to Germany and it will be very important to reconfirm how competitive we are.
"We understand that our competitors are working hard to return at the front and in Assen we succeeded in staying ahead.
"Marquez will probably be with us in the next races and we must be very careful with him."
Rossi is also expecting his teammate Jorge Lorenzo to bounce back from his below-par showing at Assen following four victories in a row.
"Jorge I'm sure will come back strong, making it even more important to work well this weekend," Rossi added.
"After Sachsenring there will be a break and it will be important to rest a bit before taking on the second part of the season."